kidturbo

Ok here's some numbers and updates from last week.

We blocked off a single scroll in each turbo to help get them spooled up and making better boost down low in the 2000's. Then added a bit more fuel and a couple degrees timing. That brought things up to 36psi with about 45psi drive pressure at around 32-3600Rpm. EGT also moved up from 1150F to 1350F with a compressor side output temperature of 370F. Torque and HP also jumped up into the 1100ft-lb / 700hp range that we were looking for here. So we made multiple 10 second runs fully loaded in this range. See below.

Everything performed flawlessly in this area. Oil pressure is running 80-90psi with temps around 120F. Will likely bypass some of that water to bring oil temps up in 160'ish at cruise here. Crankcase pressure is also under 0.5psi. The charge cooler is knocking down 370F inlet to sub 100F on all these runs. And the main cooler isn't being effected by the charge cooler load either. Overall ECT touched 205F on one long warm engine run, but typically topped out around 185F. Seawater pump is making about 12-15PSI on this charge cooler side. So everything on engine two is happy happy happy...

Now for the bad news. Our crank sensor starts taking errors above 3600Rpm when fully loaded. And the issue is most likely related to harmonics being introduced by the dyno. The factory GM ECM isn't happy with hall effect sensor signal and cuts the injectors for a complete revelation. When load is removed for that brief Ms, ECM returns to firing injectors as normal for another couple revolutions. But we are unable to get past this rpm block, even after checking all wiring and even changing dyno driveshaft. This isn't fist time the shop has experienced the problem, and has sent the dampered driveshaft out for a rebuild. But won't be back for couple weeks.

This kinda leaves us in pickle since now we need to test these turbos opened up on the big end, 4-5000Rpm range. Extrapolating current data, we end up in the mid 900hp range up there. But only if the turbos are happy, and we won't know where EGT's fall. But we have the opportunity to test using a different aftermarket ECU and harness next week. So engine #2 cam off the dyno, and engine # 1 gets tested next Wednesday. If this change resolves the misfire issues, we will go straight for the 4000Rpm range with turbos opened up. That should give us enough data to make the call on these turbos. Unfortunately these are the smallest symmetrical units available from NRE. If not where we want, may test a big single on this engine to see how it compares.

More to come next week.

Twin O/B Sonic

Killer! Your gettin there.

Couple questions that Im sure Ive already read:

1. Target red line?

2. Target boost level?

3. Target EGT?

Thanks for taking the time to post all of this and to 2187 for allowing you to.
Many w/this level $$$/time investment dont want their secrets revealed.

kidturbo

Original goal for these turbos was making a little over 50psi @ 5k with under 1500EGT.

While these turbos are certainly capable of supporting 1400hp on a gas engine, we are coming up just a little short in the mapping and exhaust flow needed to get them lit hard enough with only 400ci at half the RPM's of a typical gasser they run on.. Setting a small blower on top like Banks did it would likely accomplish this. Or stepping down in turbo size to twin 58mm should accomplish the same. Third choice, just pour a bunch of fuel to em late in the stroke like most sled puller do...

Twin O/B Sonic

payuppsucker

That's getting it done right there. Nice job!

payuppsucker

I'm thinking it's a nervous camera man.............

kidturbo

Na they'd been up in that RPM loaded at least 5 times before I shot it. Only making 2x the factory power level there.

That's called trying to hide from those freaking screaming turbo's behind a block wall. Video doesn't do it justice. I'd love to have a DB meter on em, it's +130db I'll bet. Sure know my ears hurt all night long after filming that shot..

Engine two is bolted up, and we hope to get some run time in the +4000rpm range tomorrow.

2187

Twin O/B Sonic

Easy for me. I just pull out my two hearing aids I earned from yrs of screaming two strokes

SS496

Since you already blocked off half the scroll.........can you set up a "quick spool valve" (crazy priced example here from a quick google search...https://www.ebay.com/i/162883310436?chn=ps ) would allow your mid RPM boost you need while opening up at higher RPM so you can reduce drive pressure and EGT's.

Another thing to consider is you are getting into pressure ratios (pressure ratios above 3 is starting to ask a lot from an average single centrifugal compressor...your target is in the 4.4 area) where compounds start to become a favorable option.....and will help spool response in the mid RPM range..........IIRC C15 ACERT CATs are in the 60ish PSI range with compounds at 600 HP......

Do you have compressor maps for the turbos? compressor wheel dimensions? turbine wheel dimensions?

If you know your steady state fuel rate and AFR you can accurately approximate/calculate your air mass flow rate for locating your operating point on the compressor map.


Love the project!!!!